Homeowners are working to keep the April showers outdoors, and plumbing and drain-service companies have seen their phones begin to ring..

"We had a flooded drain," said Ben Huth of Roto-Rooter. "It drains the driveway and it was packed solid with mud, leaves and sticks."

Huth said drain obstructions are a common problem in the spring, as the rains wash away winter's debris and clog drain grates.

He said the best prevention for homeowners in heavy rains like this is to ensure downspouts and drains are clear of debris, as this week's heavy rains will push many water systems to their limits.

"When we get a downpour like we've had the last few days, sewers just can't take it," he said.

In an effort to minimize the impact of heavy rains on Milwaukee's sewer system, partially as well as untreated wastewater is being diverted from the city's sanitation sites in order to retain room for future rainfall.

Black gates along the Kinnickinnic River near Sixth Street and Cleveland Avenue mark one area where MMSD said they release untreated overflow waters from the deep tunnel. A combination of rainwater and wastewater has been released since early Wednesday morning.

Milwaukee's Metropolitan Sewerage District said its two processing plants are already at capacity. The utility is releasing the untreated overflow waters in order to prevent system backups in homes and businesses.

It is allowed to perform up to six overflow diversions per year.

The deep tunnel can hold 432 million gallons of water. As of 2 p.m. Wednesday, the system had just under 300 million gallons being held.

With additional heavy rains expected for Wednesday night, the utility is preparing to make room for additional waters.

MMSD said it began discharging partially-treated overflow at 6:40 a.m. Wednesday, and is likely to continue until the rain forecast eases and the treatment facilities are able to keep up with the waters in the tunnel.